The present invention relates to valves in general and in particular a flap valve especially designed for closing an open ended material conduit. The valve is particularly adapted to high temperature installations such as the outlet of a high temperature cyclone separator such as may be used on a suspension preheater of a cement clinker producing facility.
Prior to the present invention, it was generally known to utilize flap valves at the outlet of generally vertical open ended material conduits for controlling the outlet of material from that conduit. These valves include a shaft rotatably mounted in a fixture adjacent the open end of the material conduit and a flag is operatively connected to the shaft. A counterweight exerts a rotational force on the shaft which force is transmitted by suitable means to the flap itself so that the flap is rotated toward the open end of the conduit and thus to a closed position. When material builds up within the conduit so that it has a weight sufficient to overcome the force of the counterweight, the flap will rotate to allow material to spill out of the conduit.
It has been found through experience that a common cause of failure of a flap valve is in the area of the connection of the flap to the rotatably mounted shaft. This is particularly true in high temperature applications. One means for securing the flap to the shaft includes a plurality of taper pins which extend through the shaft and flap. These pins have a tendency to work loose over a period of time with the force being transmitted between the shaft and the flap having a tendency to shear the pin. In high temperature applications, there is usually a difference in the coefficient of thermal expansion of the flap as compared to the shaft. Because the prior art has the flap fixed to the shaft, either the shaft or the flap will have a tendency to warp due to relative thermal expansion between the two parts. Because the taper pins or other means for securing the flap to the shaft put a constraint on the relative movement between the flap and the shaft, a distortion of either the flap or the shaft can occur or the means securing the flap to the shaft will fail.
By the present invention, an apparatus for securing a flap of a flap valve to the valve shaft has been provided which allows a limited relative movement between the flap and the shaft along the axis of the shaft to permit relative thermal expansion while maintaining a positive connection of the flap to the shaft and substantially preventing relative rotational movement between the shaft and the flap. In addition, the present invention allows easy replacement of the flap or the shaft or the bearings mounting the shaft. The connection of the present invention allows most of the parts to be easily manufactured at an economical price. It is particularly advantageous in its ease of assembly and disassembly.